How do fitness level and body fat affect health risks? Fitness helps to lower one’s cardiovascular risk level; gaining weight or fatness, in contrast, increases risk. Although these relationships are widely supported, there is less consensus regarding the impact of being fat but fit on health.

In a prospective observational study of 3,148 healthy adults over a 6-year time period, researchers examined the effect of fitness and fatness – separately and combined – on the development of cardiovascular disease risk factors, including hypertension, hypercholesterolemia, and metabolic syndrome. Fitness was determined using a maximal treadmill test (modified Balke protocol). Fatness was determined using percent body fat (7-site skinfold measures) and body mass index. Hypertension was defined as resting systolic blood pressure of 140 mmHg or higher, diastolic blood pressure of 90 mmHg or higher, or physician-diagnosed hypertension. Hypercholesterolemia was defined as total cholesterol of at least 240 mg/dl or physician-diagnosed hypercholesterolemia. Metabolic syndrome was defined as the presence of three or more of the following: waist circumference of over 102 cm in men or 88 cm in women, triglycerides of over 150 mg/dl, HDL-cholesterol less than 40 mg/dl in men or less than 50 mg/dl in women, blood pressure of at least 130/85 or physician-diagnosed hypertension, and fasting glucose of 100 mg/dl or physician-diagnosed diabetes.

The researchers found changes in fitness and fatness were BOTH significantly associated with the development of hypertension, hypercholesterolemia, and metabolic syndrome; lower risk was associated with maintaining or improving fitness while the opposite was true for increasing fatness.

The researchers then examined the question – can fitness compensate for the health hazards of fatness? The answer appears to be not completely. Some of the negative effects of fat gain were lessened by maintaining or improving fitness BUT were not completely eliminated. Similarly, reducing body fat compensated for some health risk associated with loss of fitness but not entirely.

Bottom line: maintaining or improving fitness ALONG WITH preventing fat gain are BOTH important for reducing risk of developing a number of risk factors associated with cardiovascular disease.

(Source: Lee D, Sui X, Church TS, Lavie CJ, Jackson AS, Blair SN. Changes in fitness and fatness on the development of cardiovascular disease risk factors. Journal of the American College of Cardiology 2012; 59:665-72.)